In recent months, spikes in birth defects, and stillborn and neonatal deaths in drilling-dense regions of Colorado and Utah has raised the attention of local communities, researchers, and public health officials. There is still much to be studied to be able to determine if there is in fact a causal link between hydraulic fracturing and adverse outcomes for infants and children. However, preliminary research is starting to suggest that there very well could be a connection. Researchers McKenzie et al. in a recent study released in February 2014, observed an association between proximity to natural gas wells within a 10-mile radius of maternal residence and a prevalence of congenital heart defects and possibly neural tube defects (an opening in the spinal cord or brain that occurs in early development) in an area of Denver, Colorado. These findings strongly suggest that rapid and thorough further investigation is warranted.

Chemicals used in the extraction, processing, distribution, transport, and waste disposal of tight oil and shale gas reservoirs can pollute the surrounding air and water. One particular phase in the tight oil and shale gas life cycle is known as high-volume horizontal fracturing (fracking). In this process, high volumes of water, sand, and chemicals are pumped under pressure into gas wells to fracture subterranean shale and force natural gas to the surface for capture and distribution. Shale gas production in the United States is projected to increase by 113% between 2011 and 2040. Pennsylvania experienced a quadruple increase in gas extraction with hydraulic fracturing between 2009 and 2011.

So what are the possible connections here and what do we know to be true concerning children’s susceptibility to toxic chemicals? There are a number of ways that unconventional natural gas extraction can impact the health of children. Children have vulnerable periods of development, both in terms of in utero exposures as well as exposures that occur after they are born. Children’s unique physiology during development makes them more susceptible to health problems. Infants and children face increased exposures, greater absorption due to a rapid metabolism, and the reduced ability to detoxify many compounds, compared to adults, making them particularly vulnerable to adverse environmental exposures.

Infants and children are also exposed to more toxic chemicals in their surrounding environment than adults. They eat more, drink more, and breathe more per unit of body weight than adults do. Studies suggest that children aged one through five years, eat approximately three to four times more food per kilogram than adults do, and that the air intake of a resting infant is twice that of an adult. Furthermore, children frequently put their hands in their mouth, which increases their ingestion of toxins in dust and soil, and they play close to the ground. This means that children will receive a higher dose of the contaminant than an adult would. Children’s detoxifying mechanisms are also developing and therefore may not protect them as well as an adult’s detoxifying mechanisms would. Kids also live longer than adults do. Should an exposure a child receives at a young age cause adverse health outcome 40 years after the exposure, it is likely the child will be alive to experience the adverse health outcome, whereas an adult exposed at age 50 may not live to see the onset of the disease.

Neural tube defects, including spina bifida (incomplete closing of the embryonic neural tube), can develop as result of chemical exposure during prenatal development of the nervous system. A well-known quartet of chemicals, usually abbreviated as BTEX, is used in millions of gallons of fracking fluids every year, and the levels in groundwater contamination spills at drilling sites studied in Colorado exceeded the National Drinking Water Standards. A study by Lupo et al found that mothers living in areas with high levels of benzene (“B” in BTEX), were more likely to have an offspring with spina bifida than were women living in areas with the lowest levels. Slama et al. reported that maternal exposure to benzene was linked with decreased fetal birth weight and decreased head circumference, both during pregnancy and at birth. Benzene acts on the skin and mucous membranes, and after absorption it can have systemic effect on the central nervous system, leading to interactions on at the systemic level.

Adults also need to be protected from environmental exposures throughout the life course as preconception exposures can influence child development. For men, environmental exposures that damage sperm can affect the health of their future offspring. For women, all the eggs a woman has during her lifetime are formed while she is still in her mother’s uterus. If an in utero exposure damages the developing fetus’ eggs, then the health of the child that fetus conceives 20 to 30 years later can be affected. Fetuses can be exposed to chemicals even inside the mother’s womb. During embryonic and fetal development, damage can occur when chemicals pass the placenta and/or blood-brain barrier. In utero exposures also impact the health outcomes of the developing fetus and with 50% of pregnancies unplanned, exposures a women experiences before she even knows she is pregnant may impact the health of her child.

Much of the conversation on the potential health effects of unconventional gas has focused on the health impacts associated with increased air pollution; either from the increased truck traffic, flaring, containment ponds and misters, etc., or from water pollution; such as from flow-back water containing naturally occurring radioactive materials, heavy metals, or the many chemicals injected into wells that may contaminate ground water. The Center for Environmental Health has more information on its website and last year issued an in-depth report on the health effects of unconventional gas extraction, specifically for pregnant women and children.

But what about other concerns, such as noise and stress, that are also quite harmful for maternal and child health? Beyond chemical exposures, there are a number of other ways that fracking can affect the health of families. For example, increased traffic volume can increase the likelihood of injuries and fatalities in a community. Other aspects of the fracking process, such as increased levels of noise from traffic and equipment can cause stress, difficulty sleeping, and psychological problems that can exacerbate physical outcomes or existing health conditions. Health outcomes related to noise pollution include hypertension, sleep disturbance, cardiovascular disease, stroke, increased aggression, depression, and cognitive impairment (such as problems with attention and recognition). Noise from road traffic has been linked with a higher risk for heart attack and heart disease.

A woman’s stress levels during pregnancy can affect the health outcomes of her child. Several studies from the University of California Irvine have looked at the effects of maternal psychosocial stress and health outcomes and have found an association between maternal stress and preterm birth, low birth weight, higher body mass index and percentage body fat, primary insulin resistance, and decreased memory performance in female children. Within communities where there is unconventional gas extraction, views on whether unconventional gas extraction is beneficial for a community or not are often very polarized, creating disputes and stress among neighbors.

No one experiences environmental exposures in isolation. What are the combined effects of multiple environmental exposures? For example, we know that air pollution effects lung development and exacerbates asthma. Now if we add stress to a person’s exposure to air pollution, it has been shown that paternal stress may have a synergistic effect in that stress amplifies the effects of traffic related air pollution on asthma. A study by Islam et al found that there is a possible common biologic pathway of stress and air pollution, and children whose parents reported a stress had children who experienced a greater detrimental effect of air pollution on their lung function volume. Unfortunately, government regulations do not require safety testing of chemicals used in fracking, nor do they require assessments of the potential impacts of multiple chemical and environmental exposures. Further, gas extraction activities are exempt from federal legislation that would otherwise regulate pollutants created by gas extraction activities including the Safe Drinking Water Act and the Clean Air Act.

There is an overall lack of systematically collected, peer-reviewed research on the health effects. of unconventional gas extraction activities. However, we do know that there are multiple toxins involved with unconventional gas extraction processes and multiple pathways of exposure to humans. Without robust research, we do not know what the long-term consequences of rapid expansion of unconventional gas extraction in the US will be on the health of women and future populations. Policy and regulation decisions are highly dependent on evidence-based information. Studies show that regulatory reforms have significantly reduced adverse health outcomes for infants and children. For example, the Clean Air Act (CAA) of 1979, resulted in air improvement standards that resulted in a 0.5% reduction in infant mortality. Legislators and regulators need to make science and health research an integral part of the development of efficient, cleaner and safer energy resources and practices.